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Re: Specify the degree of accuracy of a floating point number [message #52598 is a reply to message #52597]

Thu, 22 February 2007 09:58

Brian Larsen
Messages: 270
Registered: June 2006

Senior Member

Just to add more to the mix here:

I use the solarsoft routine round_off.pro (I will put it inline as its
short) to do this, seems to work well and its already written, which I
always like.

Brian

;+
; Project : SOHO - CDS
;
; Name : ROUND_OFF()
;
; Purpose : To round a number to a specified accuracy
;
; Explanation : Rounds the input number to the accuracy specified.
;
; Use : IDL> out = round_off(x,acc)
; IDL> out = round_off(12.278,0.01) ==> out = 12.28
;
; Inputs : x - the number to be operated on
; acc - the numerical accuracy required
;
; Opt. Inputs : None
;
; Outputs : The function value is the input rounded to the desired
accuracy
;
; Opt. Outputs: None
;
; Keywords : None
;
; Calls : NINT
;
; Restrictions: None
;
; Side effects: None
;
; Category : Util, Numerical
;
; Prev. Hist. : None
;
; Written : C D Pike, RAL, 17-May-1993
;
; Modified : Replace calls to NINT by ROUND. CDP, 17-Jun-95
;
; Version : Version 2, 17-Jun-95
;-

function round_off,num,acc

;
; check enough parameters
;
if n_params() lt 2 then begin
bell
print,'Use: num = round_off(input, accuracy)'
return,0.0
endif

;
; check for negative input
;
if num lt 0.0 then neg=1 else neg=0

;
; round off according to the accuracy required
;
num = abs(num)
if acc lt 1.0 then begin
factor = round(1.0/acc)
x = long((num+0.5*acc)*factor)/double(factor)
endif else begin
x = long((long((num+acc/2.)/acc))*acc)
endelse

;
; return in same form received
;
case datatype(num) of
'BYT': x = byte(x)
'INT': x = fix(x)
'LON': x = long(x)
'DOU': x = double(x)
'FLO': x = float(x)
endcase

if neg then return,-x else return,x

end

------------------------------------------------------------ ---------
Brian A. Larsen
Dept. of Physics
Space Science and Engineering Lab (SSEL)
Montana State University - Bozeman
Bozeman, MT 59717

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[Message index]

		Re: Specify the degree of accuracy of a floating point number By: tochaf on Fri, 23 February 2007 02:01
		Re: Specify the degree of accuracy of a floating point number By: David Fanning on Thu, 22 February 2007 13:18
		Re: Specify the degree of accuracy of a floating point number By: Brian Larsen on Thu, 22 February 2007 12:43
		Re: Specify the degree of accuracy of a floating point number By: loknath on Thu, 22 February 2007 10:57
		Re: Specify the degree of accuracy of a floating point number By: David Fanning on Thu, 22 February 2007 10:28
		Re: Specify the degree of accuracy of a floating point number By: Brian Larsen on Thu, 22 February 2007 09:58
		Re: Specify the degree of accuracy of a floating point number By: Allan Whiteford on Thu, 22 February 2007 05:05
		Re: Specify the degree of accuracy of a floating point number By: David Fanning on Wed, 21 February 2007 22:22
		Re: Specify the degree of accuracy of a floating point number By: Kenneth Bowman on Fri, 23 February 2007 08:43

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